JP2002161374A - Stainless steel sheet superior in stain resistant property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stainless steel sheet superior in stain resistant property, besides anti-adhesion property for microorganism and antibacterial activity, which are particularly preferred as building materials. SOLUTION: A method for manufacturing the stainless steel comprises; employing the stainless steel having a composition of 10% or more Cr, and 0.0001% or more and less than 1% Ag, by mass%; adjusting the surface roughness to 1 μm or more and less than 50 μm by a maximum height Ry; applying an aqueous solution of the predetermined quantity including an inorganic titanium oxide containing anatase type titanium oxide on the surface of the steel sheet; and baking it. Thereby, the steel sheet acquires a moderate hydrophlicity having a contact angle of a water droplet in the air with a surface of the steel sheet, of more than 10 degree and 50 degree or less, and having a fall initiation angle of the water droplet on the surface of the steel sheet, of less than 45 degree, at any arbitrary point of the surface of the steel sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel sheet suitable for interior and exterior of a building,
Stainless steel sheet with excellent antifouling properties that can control the adhesion and propagation of microorganisms such as slime and dirt such as oil under the weak light of indoor fluorescent light or outdoor ultraviolet irradiation environment and its production About the method.

[0002]

2. Description of the Related Art Stainless steel sheets are widely used in kitchens, bathtubs, home appliances and building materials because of their excellent corrosion resistance and clean appearance. In recent years, from the viewpoint of not only corrosion resistance but also hygiene and the environment, there has been an increasing demand for a product which suppresses the adhesion of slime and mold due to various bacteria and is excellent in antifouling property without soiling.

To meet such needs, for example, Japanese Patent Application Laid-Open No. Hei 8-60301 discloses that Cu: 0.01 to 5% by weight.
With stainless steel containing
An antibacterial martensitic stainless steel having an atomic percentage of not less than 0.2 and a ratio of the surface layer Cu concentration to the base steel Cu content of not less than 0.2 is disclosed in JP-A-8-60302.
An antibacterial austenitic stainless steel is disclosed in which a stainless steel containing 0.1% by weight is used as a base, and a Cu concentration in a surface portion is 0.1 atomic% or more and a ratio of the Cu concentration in the surface portion to the Cu content of the base steel is 0.2 or more. I have.

[0004] However, the techniques described in JP-A-8-60301 and JP-A-8-60302 cannot sufficiently suppress slime caused by various bacteria, and the antibacterial manifestation mechanism is heavy metal ions. It depends on the elution of certain Cu ²⁺ ions, which raises one problem of toxicity to the human body and one problem of loss of antibacterial properties due to depletion of ions.

In order to solve these problems, Japanese Patent Laid-Open No.
The -193218 discloses, 0.1 stainless steel material containing 1 wt% of Ti or even 0.3 to 4 wt% of Cu, 850 to 11 with H ₂ gas or H ₂ + N ₂ gas with a controlled dew point
Heat treatment at a temperature of 50 ° C to add Ti as TiO _{2 on} the material surface
A method for producing a stainless steel in which an antibacterial film containing 20% or more is formed, and Japanese Patent Application Laid-Open No. 8-193219 discloses that a dew point is controlled on a stainless steel having an effective Ti amount adjusted to 0.1 to 0.8% by weight. subjected to heat treatment for heating the H ₂ + N ₂ the temperature of 700 to 1000 ° C. in a gas, the production method of the stainless steel having antibacterial coating TiO ₂ content to form a surface layer portion containing at least 1 vol% is proposed I have. Further, JP-A-10-121222
In Japanese Patent Application Laid-Open No. H11-163, a stainless steel containing 0.2 to 3% by weight of Ti is subjected to a heat treatment of heating to 400 to 1200 ° C. in an oxidizing atmosphere to grow a thick oxide layer containing titanium oxide, and then to a reduction treatment containing hydrogen. A method for producing a stainless steel sheet exhibiting a photocatalytic action has been proposed in which heat treatment is performed at 400 to 1000 ° C. in a neutral atmosphere or electrolytic treatment is performed in an acidic aqueous solution to concentrate titanium oxide.

On the other hand, although the technology for forming TiO ₂ on the surface is not necessarily intended for stainless steel, it is mainly used for mirrors, lenses, glass, and other composite materials for imparting anti-fog properties to transparent substrates. For example, in Japanese Patent No. 2756474, a substrate and a photocatalytic film bonded to the surface of the substrate and containing a photocatalytic semiconductor material and silica are provided, and the surface of the film is used for photoexcitation of the photocatalytic semiconductor material. A composite material exhibiting hydrophilicity according to the invention also has a base material and a surface layer formed of an anatase-type titania crystal or a rutile-type crystal bonded to the surface of the base material, which is disclosed in Japanese Patent No. 2943768. A hydrophilic composite material that is made superhydrophilic so as to exhibit a water wettability of about 10 ° or less in terms of a contact angle with water in response to light excitation has been proposed. Here, the contact angle with water is α shown in FIG.
That is. In the composite material described in Japanese Patent No. 2943768, by firing amorphous titania and silica at 400 ° C. or more and converting it to anatase type titania, the contact angle with water becomes 10 degrees or less in response to photoexcitation. It is said that it exhibits hydrophilicity, improves antifogging properties, and can prevent the surface from being stained.

[0007]

The technologies described in JP-A-8-193218, JP-A-8-193219, and JP-A-10-121222 all disclose Ti contained in steel, The surface is enriched in the form of oxide by annealing, and TiO ₂
By forming a coating film (TiO ₂ rich surface layer, oxide layer containing titanium oxide), using the photocatalytic action of TiO ₂ to impart antibacterial, deodorizing, and oil-decomposing properties to steel It is.

[0008] However, stainless steel contains a large number of elements including Cr in addition to Fe, and elements other than Ti are also concentrated on the surface layer during the annealing process, so that the photocatalytic property of TiO ₂ may be hindered. Was. Further, in the method based on the concentration of Ti on the surface layer by annealing, the TiO ₂ film to be formed is almost an amorphous film having no photocatalytic action. According to the study by the present inventors, even if a crystalline TiO ₂ film of a rutile type or an anatase type was obtained by performing a heat treatment at a high temperature of 400 ° C. or more, the photocatalyst was not added to the amorphous film itself. Since no action is produced, it was found that the film was buried in the amorphous film and the function was not sufficiently exhibited. Further, the characteristics are not improved by the electrolytic treatment after the annealing treatment disclosed in JP-A-10-121222.

Further, Japanese Patent No. 2756474 and Japanese Patent No. 2943
When the technology described in No. 768 is applied to stainless steel, for example, when irradiated with ultraviolet rays, although the effect of decomposing a part of the oil attached to the surface is exhibited,
The removability of oil when wiping was performed was not always sufficient. The present invention, in view of these problems described above,
It is an object of the present invention to provide a stainless steel sheet that is particularly suitable as a building material, has microbial adhesion resistance and antibacterial properties, and is further excellent in antifouling properties.

[0010]

Means for Solving the Problems The present inventors have investigated various factors affecting the antifouling property of the surface of a stainless steel sheet in order to achieve the above object. As a result, if the surface state of the stainless steel sheet is in a state having a superhydrophilicity with a contact angle with water of 10 degrees or less, it adversely affects the antifouling property and further reduces the corrosion resistance. But
It has been conceived that the state having a hydrophilicity of more than 10 degrees is the best for improving the antifouling property.

It has been found that if such a steel sheet having such a hydrophilic surface condition is used, water can easily flow down on the steel sheet surface, and the oil on the surface can be easily removed with water. Was. That is, by imparting hydrophilicity such that the contact angle with water on the steel plate surface exceeds 10 degrees, the contact angle between the steel plate surface and the oil in water increases, and the oil on the steel plate surface is removed by water from the surface. It is easy to leave.

Further, if the surface condition of the steel sheet is adjusted so that the falling angle of the water droplet on the steel sheet surface at which the water starts to fall is a small value of less than 45 degrees, the water easily flows down, and the oil separated by the water flows down together with the water. It was conceived that the antifouling property was significantly improved. Furthermore, the present inventors have adjusted the application conditions of the inorganic titanium oxide containing anatase-type titanium oxide on the surface of the stainless steel sheet, thereby making the stainless steel sheet having a hydrophilicity such that the contact angle with water exceeds about 10 degrees. It was found that it could be a surface layer.

It has also been found that the angle at which the drop of water drops starts to be less than 45 degrees can be achieved by adjusting the surface roughness. In addition, when the amount of the inorganic titanium oxide containing anatase type titanium oxide applied to the surface of the stainless steel sheet is set to a level that does not have superhydrophilicity, the amount of titanium oxide on the surface of the steel sheet decreases, and the antibacterial effect of the titanium oxide decreases. It is feared that. The present inventors, this decrease in antibacterial action,
It has been found that it is possible to sufficiently supplement the steel sheet by adding Ag to the steel sheet to exhibit the antibacterial action of Ag.

The present invention has been completed based on the above findings and further studies. That is, the first present invention is a stainless steel sheet having a composition containing, by mass%, Cr: 10% or more and Ag: 0.0001% or more and less than 1%,
On the surface of the stainless steel sheet, at any point on the surface, a surface layer having a contact angle with water droplets in the air of more than 10 degrees and 50 degrees or less, and a falling start angle of water droplets of less than 45 degrees is characterized. A stainless steel sheet having excellent antifouling properties, and in the first aspect of the present invention, a JI
1 μm or more and 50 μm in maximum height Ry specified in SB 0601
It is preferred to have a surface roughness of less than. Here, the contact angle between the water in the atmosphere and the steel plate surface is defined as a point A where the surface of the water droplet 2 attached to the stainless steel plate 1 intersects with the surface of the stainless steel plate 1, as shown in FIG. Among the angles formed by the cutting line (tangent line) 3 drawn on the liquid surface and the surface of the stainless steel plate 1, the angle α on the side containing the water droplet is referred to.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the stainless steel sheet of the present invention will be described. The stainless steel sheet of the present invention is a steel sheet having a composition containing 10% or more of Cr and 0.0001% or more and less than 1% of Ag by mass% (hereinafter, simply referred to as%). Hereinafter, the reasons for limiting the composition of the steel sheet of the present invention will be described.

Cr: 10% or more Cr is an element necessary for obtaining corrosion resistance. To ensure sufficient corrosion resistance, Cr must be contained at 10% or more. The upper limit of the Cr content is not particularly specified, but if the content exceeds 60%, it becomes difficult to manufacture a steel sheet. In addition, from the viewpoint of manufacturability and cost, the content is preferably 35% or less.

Ag: 0.0001% or more and less than 1% Ag is an element which exerts an antibacterial action by elution of Ag ions and improves microbial adhesion and antibacterial properties. In the present invention, the content of 0.0001% or more is required. And On the other hand, if the content is 1% or more, the effect of improving the antibacterial property saturates, and an effect commensurate with the content cannot be expected. For this reason, Ag was limited to 0.0001% or more and less than 1%.

[0018] In addition to the above components, the content of Si is preferably 1.0% or less. When the content of Si exceeds 1.0%, the action of amorphous Si oxide that concentrates on the surface layer during annealing in the steel plate manufacturing process reduces oil removal in the air and water and suppresses elution of Ag ions. And the antibacterial action tends to decrease. For other steel components,
There is no particular limitation, and all stainless steel sheets in which the content of each element of Cr, Ag, or Si is within the above range are suitable.

Austenitic, ferritic,
The preferred composition range of each martensitic stainless steel sheet is shown below. Austenitic stainless steel contains Cr: 10% or more and 50% or less, Ag: 0.0001% or more and less than 1%, C: 0.001 to 0.1%, Si: 1.0% or less,
Mn: 2.0% or less, P: 0.1% or less, Ni: 6 to 15%, N:
It is preferable that the composition contains 0.001 to 0.1% and the balance is Fe and unavoidable impurities. In addition to the above composition, Mo: 3.0% or less, Cu: 1.0% or less, W: 0.
30% or less, Al: 0.3% or less, Ti: 1.0% or less, Nb: 1.0
%, Zr: 1.0% or less, Co: 0.001 to 0.5%, B: 0.
One or more of 01% or less may be contained.

In ferritic stainless steel, C
r: 10 to 50%, Ag: 0.0001% to less than 1%, C: 0.0001 to 0.1%, Si: 1.0% or less, Mn: 2.0% or less, P: 0.1% or less, N: 0.10% or less Containing, balance Fe
And a composition consisting of unavoidable impurities. In addition to the above composition, Al: 0.3% or less,
Ni: 1.0% or less, Mo: 3.0% or less, Ti: 1.0% or less, N
b: 1.0% or less, Zr: 1.0% or less, Cu: 1.0% or less,
One or more of W: 0.30% or less, Co: 0.001 to 0.5%, and B: 0.01% or less may be contained.

In the martensitic stainless steel, Cr:
10 to 19%, Ag: 0.0001% to less than 1%, C: 0.0001 to 0.1%, Si: 1.0% or less, Mn: 2.0% or less, P: 0.1% or less, N: 0.001 to 0.1% Preferably, the balance is Fe and unavoidable impurities.
In addition to the above composition, Al: 1.5% or less, Ti: 1.0%
Nb: 1.0% or less, W: 0.3% or less, Zr: 1.0% or less, Ni: 1.0% or less, Mo: 3.0% or less, Cu: 1.0% or less, Co: 0.001 to 0.5%, B: 0.01% or less One or more of these may be contained.

The stainless steel sheet according to the present invention, in addition to the above-mentioned composition, has a contact angle with water droplets in the air at an arbitrary point on the steel plate surface of more than 10 degrees and 50 degrees or less, It is a stainless steel plate having a surface layer whose start angle is less than 45 degrees. If the surface state is such that it exhibits superhydrophilicity such that the contact angle with water in the atmosphere is 10 degrees or less, part of the attached oil will be altered and adhere to the surface layer, resulting in a so-called oil stain state. May be. This is because when the surface exhibits superhydrophilicity, the affinity with the altered oil component increases. In particular, when titanium oxide is formed on the surface of the steel sheet and the contact angle with water drops in the atmosphere is reduced to 10 degrees or less, the active groups on the surface of the titanium oxide become large, and the oil stain becomes more conspicuous.

In addition, when exhibiting superhydrophilicity, corrosion resistance, which is one of the important properties for stainless steel, is sometimes greatly impaired. This is because the affinity for water, which causes corrosion, is increased, and in particular, the steel sheet is oxidized by active oxygen generated by the photocatalytic action of titanium oxide formed on the surface having superhydrophilicity. For this reason, in the present invention, the contact angle between water in the atmosphere and a steel plate is limited to more than 10 degrees. In order to sufficiently prevent oil spots, it is preferable that the contact angle between water and the steel sheet in the atmosphere is 20 degrees or more. Further, if the contact angle between water in the atmosphere and the steel sheet exceeds 50 degrees, the affinity for water is insufficient, and the separation of oil is insufficient. Limit the contact angle with the steel plate to less than 50 degrees.

The contact angle between a water droplet in the atmosphere and the steel plate surface is set to 10
In order to make it more than 50 degrees and less than 50 degrees, it is preferable to form a surface layer containing anatase type titanium oxide on the surface of the steel sheet. In the case of a normal stainless steel sheet in which the surface of the steel sheet has not been subjected to the hydrophilicity imparting treatment, the contact angle between water droplets in the air and the surface of the steel sheet is about 90 degrees. By forming a surface layer having an anatase type titanium oxide on the surface, the contact angle between a water droplet in the air and the steel sheet surface can be reduced. However, if the amount of Ti is too large in the surface layer having the anatase type titanium oxide, the contact angle between water and the steel sheet will be 10 degrees or less.

In this case, the presence of the anatase type titanium oxide in the surface layer of the stainless steel sheet is confirmed by the presence of a diffraction peak from the anatase type titanium oxide using a thin film type X-ray diffractometer. The contact angle between the water droplet in the atmosphere and the steel sheet surface can be changed by adjusting the amount of titanium oxide in the surface layer formed on the surface. In the present invention, the surface layer is determined to have a fluorescent X-ray intensity of 1 to 19 kcps (kcps: 10) by Ti obtained by X-ray fluorescence analysis (X-ray tube acceleration voltage: 40 kV, current: 60 mA).
Preferably, the layer contains ³ counts / s) of Ti.

Next, the relationship between the amount of titanium oxide in the surface layer and the contact angle between water droplets in the air and the steel sheet surface will be described based on the results of experiments conducted by the present inventors. 18.2% by mass
An austenitic stainless steel sheet having a composition containing Cr-0.0003 mass% Ag-8.3 mass% Ni was adjusted to a surface roughness of 1.3 μm with a maximum height Ry by hairline polishing. Next, an aqueous solution containing anatase-type titanium oxide was applied to the surface of the steel plate by a roll coater, and then calcined to form a surface layer containing anatase-type titanium oxide on the surface of the steel plate. At this time, the number of the aqueous solution was changed by changing the number of the roll bar coater at the time of coating, and the Ti content in the surface layer was adjusted. Next, the contact angle between water in the air and the surface of the steel sheet was measured for the obtained steel sheet.

FIG. 2 shows the relationship between the contact angle between the steel sheet surface and water droplets in the atmosphere and the amount of Ti in the surface layer. In addition, the Ti content in the surface layer was determined by a fluorescent X-ray analysis method. In X-ray fluorescence analysis, X-rays (accelerating voltage of an X-ray tube: 40 kV, current: 60 mA) are irradiated on the steel sheet surface (surface layer), and the intensity of fluorescent X-rays generated by Ti existing in the surface layer ( kcps)
It was determined as the amount (content) of Ti.

FIG. 2 shows that the amount of Ti present in the surface layer is
The contact angle between water in the atmosphere and the steel sheet surface by 10% or more but less than 19kcps
It can be seen that the temperature can be set to more than 50 degrees and less than 50 degrees. In the present invention, as described above, the surface state of the stainless steel sheet,
The hydrophilicity is adjusted so that the contact angle with a water droplet in the atmosphere is more than 10 degrees and not more than 50 degrees, but by making such a surface state, generation of oil stains is eliminated. In such a state, the contact angle with the oil droplet in water becomes large, for example, the contact angle with the salad oil in water exceeds 90 degrees, and the wiping property of the oil becomes good. In the case of a normal stainless steel sheet having a contact angle between water droplets in the atmosphere and the steel sheet surface of about 90 degrees, the contact angle between the salad oil and the steel sheet surface in water is less than 90 degrees.

The larger the contact angle between the salad oil and the surface of the steel sheet in water, the more easily the oil can be removed, and the more easily the oil can be wiped off. The contact angle between the steel sheet surface and water in the atmosphere is 10
In the case of those having super hydrophilicity of less than degree, the contact angle between the salad oil and the steel sheet surface in water is about 100 degrees. If the contact angle between the salad oil and the steel plate surface in water is 100 degrees or more, the oil can be easily removed by wiping. Therefore, from the viewpoint of wiping oil, it is more advantageous to have superhydrophilicity. However, when it has superhydrophilicity, the problem of oil stain occurs as described above. For this reason, in the present invention, the surface state (surface layer) of the stainless steel sheet is adjusted so that the contact angle with water in the atmosphere is more than 10 degrees and 50 degrees or less.

The contact angle between the salad oil and the steel sheet surface in water can be measured, for example, using a fully automatic contact angle meter C manufactured by Kyowa Interface Chemical Co., Ltd.
It can be measured using an AW type three-part set. FIG. 3 schematically shows a method of measuring a contact angle between a salad oil and a stainless steel plate in water. For the measurement, pure water 5 is put into the glass cell 4, and a measurement sample (stainless steel sheet 1) is set in the pure water 5 with the measurement surface facing downward. The cylinder 6 is filled with salad oil to be used for the measurement, and an inverted needle 7 (key-type in which the liquid flows out from the bottom to the top) is connected. With these sets, oil droplets are discharged from the tip of the inverted needle 7 and adhere to the surface of the sample in water (the lower side is the measurement surface), and the contact angle between the sample (stainless steel plate 1) and the oil droplet 22 is measured. In addition,
The method for measuring the contact angle is the same as the method for measuring the contact angle with water in the atmosphere.

Further, the stainless steel sheet of the present invention has a surface layer in which the falling angle of the water droplet on the steel sheet surface is 45 degrees or less, in addition to having the contact angle with the water droplet in the atmosphere as described above. If the falling angle of the water droplet is 45 degrees or less,
When moisture comes into contact with the surface, removal (falling) from the surface becomes easy, and dirt is easily removed along with the moisture. On the other hand, when the falling angle of the water droplet exceeds 45 degrees, moisture easily remains on the surface, and dirt along with the moisture easily remains on the surface.

In order to make the falling angle of water droplets on the steel sheet surface 45 degrees or less, it is preferable that the surface roughness (surface layer) of the steel sheet surface is less than 50 μm in maximum height Ry. The falling angle of water droplets on the steel sheet surface is the angle at which water drops (pure water) are placed on the surface of the steel sheet while the steel sheet surface is horizontal and when the steel sheet surface is tilted from this state Say.

In order to make the surface roughness of the steel sheet less than 50 μm in maximum height Ry in a state where the surface layer containing anatase type titanium oxide is formed, as described later, anatase type titanium oxide is used. The surface roughness of the stainless steel plate before applying the aqueous solution may be adjusted by rolling with a dull roll, sand blasting, liquid honing, a polishing belt or the like so that the maximum height Ry is less than 50 μm.

The surface roughness of the steel sheet is 1 at the maximum height Ry.
If it is less than μm, it becomes impossible to secure anti-glare properties and it is not suitable for building materials. Further, it is difficult to form titanium oxide uniformly on the surface of a steel plate having a maximum height Ry of less than 1 μm. For this reason, it is preferable that the surface roughness of the steel sheet surface be 1 μm or more and less than 50 μm in Ry.

Next, a method for manufacturing a stainless steel sheet according to the present invention will be described. First, a stainless steel molten steel adjusted to the above composition is melted and made into a rolled material by a generally known casting method such as a continuous casting method, and hot-rolled, according to a conventional method such as cold rolling, a stainless hot-rolled steel sheet or Stainless steel cold rolled steel sheet. Then, the surface roughness of these stainless steel plates was
It is preferable to adjust the maximum height Ry so as to be 1 μm or more and less than 50 μm. The adjustment of the surface roughness can be achieved by subjecting a stainless steel plate to a treatment such as rolling with a dull roll, sand blasting, liquid honing, or a polishing treatment using a polishing belt such as a hairline or No. 4.

If the maximum height Ry is 50 μm or more, the surface roughness of the stainless steel plate is too rough, so that the dirt in the recesses accumulates, making it difficult to remove the dirt. Furthermore, the falling start angle of the water droplet becomes too large, and the antifouling property decreases. On the other hand, if the surface roughness is less than 1 μm in maximum height Ry, it becomes difficult to uniformly apply an aqueous solution containing an inorganic titanium oxide to the surface, and it is impossible to impart uniform antifouling properties. Furthermore, it causes uneven color tone and is unsuitable for use as a building material. If the surface roughness is less than 1 μm in the maximum height Ry, the anti-glare property cannot be ensured.

Next, the stainless steel sheet adjusted to the above-mentioned surface roughness is preferably heated to reduce the steel sheet surface temperature by 50%.
After the temperature is set to not lower than 90 ° C. and lower than 90 ° C., an aqueous solution containing an inorganic titanium oxide containing anatase type titanium oxide is applied to the surface of the steel sheet. When the surface temperature of the steel sheet when applying the aqueous solution containing the inorganic titanium oxide is 90 ° C. or higher, the aqueous solution is dried at the same time as the application, and it becomes difficult to apply the aqueous solution uniformly, which causes uneven color tone. . On the other hand, when the steel sheet surface temperature is lower than 50 ° C., uneven drying occurs, which causes uneven color tone.

The method of applying the aqueous solution does not need to be particularly limited, and may be performed according to a conventional method such as a roll coater. The amount of the aqueous solution containing the inorganic titanium oxide containing the anatase type titanium oxide is determined by the relationship between the concentration of the inorganic titanium oxide in the aqueous solution, the amount of the aqueous solution applied, and the amount of Ti in the surface layer after firing. Determined in advance, and the surface layer is Ti
The concentration of the inorganic titanium oxide in the aqueous solution and the application amount of the aqueous solution may be determined so that the amount is contained. Examples of the aqueous solution containing an inorganic titanium oxide containing anatase type titanium oxide include a commercially available titanium dioxide dispersion containing anatase type titanium oxide (TAO Co., Ltd., TAK-
70-85, JTAK-50-85, JTAK-50-170), a solution obtained by mixing silica-containing titania sol (tetraethoxysilane (manufactured by Wako Pure Chemical Industries, Ltd.)) and anatase-type titania sol (manufactured by Nissan Chemical Industries, TA15) with pure water, etc. Is preferably used.

Further, instead of applying an aqueous solution containing an inorganic titanium oxide containing an anatase type titanium oxide,
There is no problem with the method of embedding the anatase type titanium oxide in the surface layer by a roll or the like. Next, the stainless steel plate is preferably subjected to a baking treatment for baking inorganic titanium oxide containing anatase type titanium oxide on the surface.
The baking temperature is preferably 100 ° C. or more and less than 400 ° C. If the baking temperature is 400 ° C. or higher, elements in the steel are concentrated on the steel sheet surface, and the Ti content in the surface layer is reduced, thereby adversely affecting the photocatalytic action of the anatase type titanium oxide. On the other hand, if the baking temperature is lower than 100 ° C., drying is insufficient and uneven drying occurs, resulting in uneven color tone. For this reason, the baking temperature is preferably limited to 100 ° C. or more and less than 400 ° C. The temperature is more preferably lower than 250 ° C. The baking time is preferably set to 20 to 60 minutes. If it is less than 20 min, drying unevenness will occur. In the above-mentioned temperature range, drying takes place sufficiently for 60 min, so that baking beyond 60 min is meaningless.

[0040]

EXAMPLES (Example 1) Molten steel having the composition shown in Table 1 was smelted by a converter and made into a slab by a continuous casting method. Then, after heating these slabs, they are hot-rolled to a thickness of 4 mm.
mm hot rolled sheet. After annealing and pickling these hot-rolled sheets, cold-rolled sheets having a thickness of 1.0 mm were formed by cold rolling. Finish annealing and pickling were performed on these cold-rolled sheets to obtain cold-rolled annealed sheets.
The final annealing temperature was 1100 ° C for austenitic stainless steel and 800 for martensitic stainless steel.
° C, and 850 ° C for ferritic stainless steel.

The obtained cold-rolled annealed plate was ground with a polishing belt.
Polishing was performed to obtain a steel sheet having a surface roughness shown in Table 2. By the way,
These cold-rolled annealed sheets were placed in a NaOH solution at a temperature of
And 10A / dm ^TwoPerformed alkaline electrolytic degreasing under conditions of × 30 seconds
Then, after drying with a dryer, it was heated to 80 ° C. This temperature
Neutral water on inorganic titanium compounds
The solution was applied with a bar coder.

The neutral solution of the inorganic titanium compound may be a commercially available titanium dioxide dispersion containing anatase type titanium oxide (TAK-70-85, manufactured by TOA Corporation).
It was used. The cold-rolled annealed sheet coated with the neutral solution of the inorganic titanium compound was then subjected to a baking treatment at 250 ° C. × 30 ° C. For the baking treatment, a heating chamber under an air atmosphere was used.

With respect to the steel sheet thus obtained,
(1) Structural analysis of surface layer, (2) Quantification of Ti content in surface layer, (3) Measurement of surface roughness, (4) Measurement of contact angle between steel sheet surface and water droplet in air, (5) ) The contact angle of oil on the steel plate surface in water was measured, and (6) the falling angle of water droplets on the steel plate surface was measured. The measuring method was as follows. (1) Structural analysis of surface layer Thin film X-ray diffractometer (RU-300 / 2655A1: Rigaku Corporation)
, 18 kW Cu, rotating anti-cathode), and irradiating the surface layer of the steel sheet with X-rays. From the obtained diffraction peaks, the components were identified with a JCPDS card. The obtained diffraction peaks could be distinguished from those from anatase-type titanium oxide, those with a mild peak presumed to be amorphous, and those without any diffraction peaks from these oxides. . Then, the presence or absence of the anatase type titanium oxide was confirmed from the identification result of the diffraction peak. (2) Determination of Ti content in the surface layer For each stainless steel plate, using a fluorescent X-ray diffractometer (X-ray tube: 40 kV, 60 mA), the acceleration voltage of the X-ray tube: 40 kV, current: 60 mA X-ray irradiation was performed, and the fluorescent X-ray intensity (kcps) of the generated Ti was measured and defined as the Ti content. (3) Measurement of surface roughness For each stainless steel plate, using a contact type surface roughness meter,
The maximum height Ry was determined in accordance with the provisions of JIS B O601. (4) Measurement of the contact angle between the steel sheet surface and water droplets in the atmosphere. Each stainless steel sheet (measurement sample) is placed on a 90-degree rotating stage that can rotate from horizontal to vertical, with the stage being horizontal. A water drop (pure water) is dropped and adhered to the surface of the stainless steel plate in the atmosphere, and a fully automatic contact angle meter CA-W is used.
Using a mold (manufactured by Kyowa Interface Chemical Co., Ltd.), the contact angle (α in FIG. 1) between the sample and the water droplet was measured. (5) Measurement of contact angle between steel plate surface and salad oil in water Pure water is placed in a glass cell, and a measurement sample (stainless steel plate) is set in pure water with the measurement surface (stainless steel plate surface) facing downward. The cylinder is filled with salad oil (manufactured by Nisshin Co., Ltd.) to be used for the measurement, and an inverted needle (a key-shaped type in which liquid flows out from bottom to top) is connected. Oil droplets were ejected from the tip of the inverted needle and allowed to adhere to the surface of the sample in water (the lower side is the measurement surface) (see FIG. 3). And a fully automatic contact angle meter CA-
The contact angle (α in FIG. 3) between the surface of the steel sheet and the salad oil was measured using a W-type (Kyowa Interface Chemical Co., Ltd.) three-phase component set. (6) Measurement of falling angle of water droplet on steel plate surface Each stainless steel plate is placed on a rotating stage with the stage being horizontal, and water droplets (pure water) are dropped and adhered to the stainless steel plate surface in the atmosphere. Then, the stage was rotated from the horizontal, and the moment when the water droplet started to fall was captured using a CCD camera, and the angle at that time was obtained, and the angle was determined as the falling angle.

Next, the obtained stainless steel sheet was tested for stain resistance and corrosion resistance. The test method was as follows. (7) Antifouling test An air exposure test was performed as an antifouling test. A test piece collected from each stainless steel plate was exposed to the air for one month, and the amount of deposits on the surface of the test piece was measured. The 2B-finished SUS 304 steel sheet was simultaneously subjected to an atmospheric exposure test and used as a reference steel sheet. The antifouling property of each stainless steel sheet was evaluated as x when the amount of deposits was greater than the amount of deposits on the reference steel sheet, and as を when the amount was less than the amount of deposits. (8) Corrosion resistance test A corrosion test specimen was collected from each stainless steel plate and subjected to a salt-dry / wet combined cycle test. After the test, the rust area of the test piece was measured by visual observation, and the rust area ratio was determined. The corrosion resistance was evaluated as ○ if the rust area ratio was 5% or less, and × if it exceeded 5%.

The test cycle of the salt-dry / wet combined cycle test was as follows. Test cycle: 0.5 hour salt spray (5% NaCl water, temperature: 35 ° C) → dry for 1.0 hour (humidity ≤ 40%, temperature: 60 ° C) → wet for 1.0 hour (humidity ≥ 95%, temperature: 40 ° C) After 10 cycles, the surface was observed after the test.

Table 2 shows the results of these measurements.

[0047]

[Table 1]

[0048]

[Table 2]

In any of the examples of the present invention, the contact angle between the steel sheet surface and the water droplet in the atmosphere is more than 10 degrees and 50 degrees or less, the contact angle between the steel sheet surface and the oil in water is more than 90 degrees, and Has a fall start angle of less than 45 degrees, and has good antifouling properties. Furthermore, it also has good corrosion resistance. On the other hand, the comparative examples out of the range of the present invention have deteriorated antifouling property and / or corrosion resistance.

Steel sheet No. 1, which is a comparative example, has a low Ti content in the surface layer, a contact angle of water droplets in the air of 56 degrees, and a contact angle between the steel sheet surface and oil in water of less than 90 degrees. Antifouling property is reduced. In addition, steel sheets No. 5, No. 9, and No. 12 had too much Ti content in the surface layer, and the contact angle of water droplets in the atmosphere was low.
When it is less than 10 degrees, it is out of the range of the present invention, and since it has superhydrophilicity, oil stain occurs, and the antifouling property is reduced. There was also a problem in corrosion resistance.

Further, the steel plates No. 6 and No. 13 have a large maximum height Ry on the steel plate surface, and the falling angle of the water droplet falling is 45 degrees or more, which is out of the range of the present invention. I have. Also,
For the steel sheets No. 7 and No. 14, the Ag content in the steel was out of the range of the present invention,
The antibacterial property of Ag is not obtained, the antimicrobial resistance is poor, and as a result, the antifouling property is deteriorated. In addition, steel plate No. 10
The Cr content in the steel is out of the range of the present invention, and the corrosion resistance is insufficient.

[0052]

According to the present invention, a stainless steel sheet having excellent antifouling properties, and particularly suitable as a building material, can be easily produced, and has a remarkable industrial effect.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a method for measuring a contact angle.

FIG. 2 is a graph showing the relationship between the fluorescent X-ray intensity of Ti in a stainless steel sheet surface layer and the contact angle between the surface of the stainless steel sheet and water droplets in the atmosphere.

FIG. 3 is an explanatory diagram showing a method for measuring a contact angle between an oil droplet in water and a stainless steel plate (sample).

[Explanation of symbols]

 1 Stainless steel plate 2 Water drop 22 Oil drop 3 Tangential wire 4 Glass cell 5 Pure water 6 Cylinder 7 Reverse needle

Continuation of the front page (72) Inventor Osamu Furukun 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term in Technical Research Institute, Kawasaki Steel Co., Ltd. 4K044 AA03 BA12 BC02 CA07 CA15 CA53 CA62 CA67

Claims (2)

[Claims] 1. In mass%, Cr: 10% or more, Ag: 0.0001%
A stainless steel sheet having a composition containing not less than 1% and a contact angle with a water drop in the atmosphere at an arbitrary point on the surface of the stainless steel sheet at more than 10 degrees and not more than 50 degrees, and the drop of the water drop A stainless steel sheet having excellent antifouling properties, having a surface layer having a starting angle of less than 45 degrees. 2. With the surface layer, a maximum height R
The stainless steel sheet according to claim 1, wherein the stainless steel sheet has a surface roughness of 1 µm or more and less than 50 µm in y.